FIG. 1 is a somewhat schematic plan view of a conventional substrate processing tool 11 of the type which is used to apply semiconductor manufacturing processes to substrates such as silicon wafers or glass plates. As is familiar to those who are skilled in the art, silicon wafers may be used for fabrication of semiconductor devices such as processors, memory devices, etc. Glass plates may be processed to manufacture flat panel displays for use as computer monitors, television displays or the like.
The processing tool 11 includes a centrally located transfer chamber 13, to which process chambers 15 are coupled. In each of the chambers 15, a semiconductor fabrication process such as thin film deposition, oxidation or nitridization, etching, or thermal or lithographic processing, may be performed. Substrates to be processed in the processing tool 11 are introduced into the processing tool 11 via at least one load lock chamber 17 coupled to the transfer chamber 13. A substrate handling robot 19 is installed in the transfer chamber 13 to transfer substrates among the load lock chamber 17 and the process chambers 15.
It is known to equip a transfer chamber of a processing tool with sensors for detecting whether a substrate is present and is properly positioned for loading into one of the process, load lock, or other chambers coupled to the transfer chamber. In one conventional processing tool which is adapted to process rectangular glass plates, and which has seven chambers coupled to it (e.g., six process chambers and a load lock chamber such as is shown in FIG. 1), a total of twenty-eight sensors are employed. That is, a group of four sensors is arranged in the transfer chamber adjacent each opening in the transfer chamber which connects to a respective one of the seven chambers coupled to the transfer chamber. Each of the four sensors in a group of sensors is provided to detect the presence and correct positioning of a respective corner of the rectangular glass plate. The group of four sensors adjacent a particular process chamber or load lock chamber may be used to confirm that a glass plate is properly positioned adjacent the process chamber or load lock chamber, before motion of the substrate handling robot is initiated to load the glass plate into the process chamber or load lock chamber.
Although conventional sensor arrangements perform satisfactorily for their intended purpose, it would be desirable to reduce the cost of providing sensors and installing them in a transfer chamber.